Abstract

Residual absorption in optical coatings and materials is directly measured by means of the laser-induced deflection (LID) technique. For transmissive coatings a measurement strategy is introduced that allows for the separation of different absorptions of the investigated sample (bulk, coating, surface) by use of only one sample. Laser irradiation yields absorption values between 2×10−3 and 2.9×10−2 for antireflecting and highly reflecting (HR) coatings at 193nm and 30.6×10−6 for a HR mirror at 527nm. Use of laser-induced fluorescence at 193nm excitation reveals trivalent cerium and prasodymium and hydrocarbons in different single layers and coatings. In addition to correlation with absorption data, the influence of a high fluorescence quantum yield on the absorption measurement is discussed.

Dependence of the calibration coefficients for bulk and thin-film and surface absorptions on the probe beam position along the sample length. The substrate material is CaF2 with a geometry of 20⁢mm×20⁢mm×10⁢mm. Measurements were taken with a double probe beam passing through the sample.

Dependence of the calibration coefficients for bulk and thin-film and surface absorptions on the probe beam position along the sample length. The substrate material is fused silica with a geometry of 20⁢mm×20⁢mm⁢×20⁢mm. Measurements were taken with a quadruple probe beam passing through the sample.

LIF spectrum,
excited at 193nm with a fluence of H=15mJ/cm2,
for a 50nmLaF3 single layer deposited onto a silicon substrate (sample 6 in Table 1). The spectrum was taken at a recording duration of 10 μs.

LIF spectra of an AR coating on a silicon substrate (sample 7 in Table 1)
showing the change in the hydrocarbon fluorescence peaks around 290 and 430nm that is due to ArF laser irradiation at a fluence of H=15mJ/cm2.
The spectra were taken at a recording duration of 100 ns. The spectrum after ArF laser irradiation is rescaled for better viewing.

LIF spectra of two different HR coatings (samples 3 and 4 from Table 1).
The excitation wavelength is 193nm with a fluence of H=15mJ/cm2.
The spectra were taken at a recording duration of 100 ns. The spectrum for sample 3 is rescaled for better viewing.